Alfred Molina is exploring. He's just discovered a grand TV set inside a grand cupboard inside his grand suite in a central London hotel. "Blimey!" he says. "Fan-tas-tic!" A great lolloping hulk of a man, he still has a toddler's sense of wonder. We find another cupboard with a mini-bar, and another with a photocopier. "Ooh! Isn't this fantastic?" Then he laughs. And when he laughs, he really laughs - a pornographic "Heh-heh-heh!" followed by a choking "Chhhhhhhhhhhhhh!" "Ah, you thought I was living here? Nooooah! Nooooah! I've only just walked in here myself."

Molina, now 51, has been a successful actor for more than 30 years, and is about to become a superstar. In Spider-Man 2 he plays the ultimate baddie - nothing new there, except this movie cost $200m and has already grossed more than that in its first eight days of US release, breaking all records.

The body of Dr Otto Octavius, half-man, half-octopus, is staring down from hoardings worldwide. Doc Oct is a Faustian figure who sells his soul to science. But as with most of the baddies or screwups or buffoons Molina has played (from Joe Orton's murderous lover in Prick Up Your Ears to the coked-out drug dealer in Boogie Nights, the suicidal comedian Tony Hancock in the biopic, or the uptight local politician in Chocolat) he retains a degree of humanity.

Molina often plays foreigners. His father was Spanish, his mother was Italian, he looks Jewish (though he's not) and he does great accents. I tell him that the first time I noticed him was as the hapless schlemiel in Les Blair's film The Accountant.

"Yeah, I've given a few good Jews. I've given a few good Arabs, too. Good Jew, good Arab, good European, good South American, I give good Cuban. Heh-heh-heh-heh-heh. Generally speaking I give good foreign. Heh-heh-heh-heh-heh."

And his English? "I don't give good English really." Why not? "I was always like the foreign geezer. Even at drama school if there was a part of some eastern European thug it would be me."

It's easy to forget that Molina is English. He was brought up by his parents in west London. When he was young his mum worked as a cook and his dad as a chauffeur and odd-job man for a Jewish family. Both parents tried hard to assimilate (his father even making cackhanded attempts at slang) but never fully succeeded. "I've been thinking about this a lot recently, partly because I've been playing Tevye [in Fiddler on the Roof on Broadway]. When I was young I never really felt English."

It wasn't just his background that was different. He didn't look like most actors. As a child, he'd been bullied for his size. "When I was younger I was always big, I was a fat boy at school. I had an early growth spurt, and when I went to secondary school I was tall enough to be a policeman. I was always a bit weird-looking and I carried myself in a weird way, so when I was at drama school I was never considered for the romantic parts."

His heroes were also outsiders. "The big stars I felt a kinship with were never the romantic leads. It wasn't Steve McQueen or Robert Redford - it was people like Walter Matthau and Anthony Quinn. My big hero was Tommy Cooper."

There is a lovely warmth and ease to Molina. When he was in his 20s he looked old for his age; now he looks young. His hair is thick and wavy and black, his eyes (so often cold and menacing on screen) are a soft, dopey brown. He's an unlikely mix - oafish, sexy and a little maternal.

It's funny that he so often plays hard cases when he's such a teddy bear. "I'm an actor," he says, coming over all thespish.

It does make life much more interesting, though. If he was Brad Pitt or Tom Cruise he'd have to play Tom Cruise or Brad Pitt in every studio film he made. "In America it's odd because when you talk to journalists they ask things like 'Does it bother you that people kinda often refer to you as, you know, aren't you the guy that played so and so?' And I'd say, 'No, it's actually a compliment if the actor is disappearing and what remains in the memory is the performance.' That's got to be good, innit?"

The blessing of being a character actor is that he's always doing different stuff. At the moment he has the perfect balance - two independent movies (Jim Jarmusch's upcoming Coffee and Cigarettes, and Nick Hurran's funeral parlour comedy Undertaking Betty) offset by Spider-Man 2. The curse of being a character actor is that he has to put so much time into every role. "You can't just turn up and put on a suit. You know, you've got like a three-hour make-up job and a hump - Heh!-Hehheh! - and a limp. Heh!-Hehheh!"

Throughout his life, Molina has defied expectations in a gentle, unassuming way. He prefers clothes shopping to football and has set up a girly-man group with fellow actor Gary Oldman for fellow heterosexual girly-men. He married the actor and author Jill Gascoigne, who is 16 years his senior, and they have lived in Los Angeles for the past 12 years.

Moving to LA made sense, he says. After he returned from a brief stint in Hollywood in the early 1990s he sat in London for eight months and was offered one radio play. "I thought, 'Fuck this - I'm going back. I can earn some money.' Jill was very good. She said, 'Let's go back, see what happens - it's an adventure.' Our kids were grown up [between them they have three children from previous relationships]. Next thing you knew, we'd bought a house and had two dogs."

What kind of dogs? "Ah, just a couple of mutts, Nancy and Charlie. I love ugly dogs that no one else wants. We always named our dogs after jazz musicians - Charlie Parker and Nancy Wilson. A little pretentious thing! A very right-on mate of mine asked, 'Why did you call him Charlie?' And I said I called him Charlie after Charlie Parker, and he went, 'Oh dear! Why? Because he's black?' I said 'No, because he plays the fucking saxophone!' Heheheheheh! Chhchcchchchch ... Hhuhuhhuh!"

People have often criticised his life choices. For example, he says, when he and Jill got together the tabloids had a field day depicting her as a cradle-snatcher and him as a toyboy.

There have been tough times - Gascoigne has suffered severe depression and kidney cancer. But 22 years on, their relationship is still strong. "Our marriage did take a few people by surprise, but what really surprised them was the fact that it lasted." I ask Molina what has given him most happiness. "Jill," he answers instantly.

People also sniffed at their move to LA. "A lot of my English friends used to say, 'Ach, how can you live in Los Angeles? It's so superficial.' And I'd find myself saying things like, 'Well, I'm a very superficial person, so it suits me fine.' "Have they been out to see him in LA? "Oh yeah, and they all love it. They all go, 'Ach, couldn't live here. Can we come and stay?' Hehhehhehhehhehehuhchhhhhh! 'Got a pool?'"

Look, he says, Los Angeles is just an industry town, and if you want to live the quiet life it's as easy to do it here as anywhere else. "I'm sure some people would think our life is really rather mundane. I work and come home and have me dinner."

Does he think his life is mundane? He thinks about it and smiles. "No, I love it. At the risk of sounding smug, I love my life."